Liquid hydrocarbon mediums, such as crude oils, crude fractions, such as naphtha, gasoline, kerosene, jet fuel, fuel oil, gas oil and vacuum residuals, often contain metal contaminants that, upon processing of the medium, can catalyze undesirable decomposition of the medium or accumulate in the process residue. Accumulation of iron contaminants, like others, is undesirable in the product remaining after refinery, purification, or other processes and, accordingly, diminishes the value of such products.
Similar iron contamination problems are experienced in conjunction with other liquid hydrocarbons, including aromatic hydrocarbons (i.e., benzene, toluene, xylene), chlorinated hydrocarbons (such as ethylene dichloride), and olefinic and naphthenic process streams. All of the above petroleum feedstock and fractions and petrochemicals are referred to herein as "liquid hydrocarbon mediums."
Iron in such liquid hydrocarbon mediums may occur in a variety of forms. For example, it may be present as a naphthenate, porphyrin, or sulfide. In any case, it is troublesome. For example, residuals from iron-containing crudes are used, inter alia, to form graphite electrodes for industry. The value and useful life of these electrodes is diminished proportionately with the level of undesirable iron contamination.
Additionally, in many processes iron-containing catalysts are used which may carry over with the product during purification. Iron catalyst contaminated product leads to deleterious effects.